1. Field
Embodiments of the present invention relate to a multi pass type color image forming apparatus that forms an image based on a position of an intermediate transfer belt and a control method thereof.
2. Description of the Related Art
A color image forming apparatus may be classified as a multi pass type color image forming apparatus that rotates a photoconductor several times to form a color image or a single pass type color image forming apparatus that rotates a plurality of photoconductors once to form a color image.
The multi pass type color image forming apparatus generally includes an intermediate transfer belt that overlaps color developing agent images formed on the photoconductor to form a primary transfer image and secondarily transfers the primary transfer image to print media.
The developing agent images may be separately formed on the photoconductor by corresponding developers and then transferred to the intermediate transfer belt in an overlapping fashion. In order to obtain a uniform primary transfer image having no color registration error between the respective color developing agent images when the color developing agent images formed on the photoconductor are transferred to the intermediate transfer belt in an overlapping fashion, therefore, it may be necessary to transfer the respective color developing agent images to the same position of the intermediate transfer belt.
Conventionally, a position recognition hole indicating a home may be formed at the intermediate transfer belt, and the position recognition hole is sensed by a sensor so that the sensed result is used as a criterion to form an image on the photoconductor. That is, exposure time points of the respective colors are decided based on the home to align color front ends.
During consecutive printing of several pages in the multi pass type color image forming apparatus, an image primarily transferred to the intermediate transfer belt is secondarily transferred to paper, and then image wastes are removed from the intermediate transfer belt before next page printing so that the next page image is transferred to the intermediate transfer belt. A cleaning blade contacts the intermediate transfer belt to remove image wastes from the intermediate transfer belt.
During cleaning of the intermediate transfer belt, a load of, for example, 5 to 20 N is applied to the intermediate transfer belt. This load changes the position of the intermediate transfer belt. As a result, a color registration error may be generated.
When a page is printed, and the position recognition hole is sensed to print the next page, an exposure unit and developers are controlled to form a first color developing agent image, e.g. a yellow developing agent image, on the photoconductor and to transfer the developing agent image to the intermediate transfer belt. When the position recognition hole is sensed at this time, the yellow developing agent image is formed on the photoconductor and, at the same time, the cleaning blade, which is in contact with the intermediate transfer belt to clean the intermediate transfer belt, is separated from the intermediate transfer belt to finish cleaning.
Whenever the position recognition hole is sensed, other color developing agent images are formed on the photoconductor, and the developing agent images are transferred to the intermediate transfer belt, to which the yellow developing agent image has already been transferred, in an overlapping fashion.
However, when the first color developing agent image, e.g. the yellow developing agent image, is formed, the cleaning blade is not completely separated from the intermediate transfer belt unlike the other color developing agent images. Thus, the rotational velocity of the intermediate transfer belt is decreased due to friction caused by contact with the cleaning blade. As a result, a color registration error between the respective color developing agent images transferred to the intermediate transfer belt is generated. That is, yellow developing agent image transferred to the intermediate transfer belt is not aligned with magenta, cyan, and black developing agent images transferred to the intermediate transfer belt.